In recent years, weight reduction of vehicles as well as vehicle body stiffness has been demanded for overall improvement of drivability, livability, fuel efficiency, and the like. Since the required vehicle body stiffness and strength of the vehicle-body structure are different according to the specifications and destinations of the vehicles, numerous variations adapted for the vehicle specifications and the like are necessary.
Conventionally, a vehicle-body structure in which an extension is arranged in the front-rear direction of the vehicle body to partition off the inside of the side sill (for example, as disclosed in Patent Literature 1) and a vehicle-body structure in which bulkheads are arranged in a side-sill cross section to block up closed cross sections (for example, as disclosed in Patent Literature 2) are known as means for increasing the rigidity of the side sill in the vehicle body.
In the vehicle-body structure disclosed in Patent Literature 1, a lower end portion of a center pillar inner panel 8 is arranged to pass through a side-sill cross section, and overlap with a floor compartment 7 and a side-sill inner 9, and those three parts are joined together.
Thereby, collapse deformation and compression deformation of the side sill in the vertical direction is suppressed, so that the stiffness and the strength of the side sill are increased.
In the vehicle-body structure disclosed in Patent Literature 2, a bulkhead 17 is arranged in the side-sill cross section at the intersection of a side sill 16, a center pillar 32, and a cross member 57.
Thereby, the bulkhead 17 can suppress the sectional deformation and distortion of the side sill 16 to improve the stiffness and the strength of the side sill. In addition, the bulkhead 17 can efficiently transmit a load of a side collision from the center pillar 32 and the side sill 16 through the bulkhead 17 to the cross member 57, and can suppress the amount of deformation of the interior space in the event of a side collision.